transmitter.) The blanking level (300 mV) yields 73% (in an ideally linear transmitter). Usually the figure 75% is found to be acceptable. The highest modulating signal at white (1000 mV) yields only 10% of the carrier. (so called residual carrier). Sometimes 12.5% is used as the residual carrier so the output power applied to the antenna system is considerably lower than the nominal power. The thermal power which can be measured by a microwave power meter depends on the program content as well as the residual carrier and sync depths. Ratio of thermal power to nominal power Since the program content is variable, the thermal power varies during the transmission. However, for testing purposes a standard line waveform can be applied to the transmitter. Usually line waveforms corresponding to 350 mV or 300 mV black image (and without field sync) are applied to the input of the transmitter. For System B, the duration of the black level 300 mV (together with the front and back porches), is 59.3 μs and it corresponds to 73% of maximum voltage level. The duration of the sync pulse is 4.7 μs. The total duration of the line is 64 μs. So the maximum thermal power applied to the antenna system is 57% of the nominal power, even in the black scene. In normal program content this ratio may be around 25% or less. References Television technology Broadcast transmitters Radio transmission power